Experimentally ruling out joint reality based on locality with device-independent steering

Abstract

As an essential concept to understand the world, whether the real values (or physical realities) of observables are suitable to the physical systems beyond classic has been debated for many decades. Although standard nogo results based on Bell inequalities have ruled out the joint reality of incompatible quantum observables, the possibility of giving simple yet strong arguments to rule out joint reality in any physical system (not necessarily quantum) with weaker assumptions and less observables, has been explored and proposed recently. Here, we perform a device-independent experiment on two-qubit superconducting system to show the joint reality of two observables is incompatible with locality under weaker assumption of the reality of observables in a single space-time region (or single qubit). Our results clearly show the violation of certain inequalities derived from both linear and nonlinear criteria. In addition, we study the robustness of the linear and nonlinear criterion against the effect of systematic decoherence. Our demonstration opens up the possibility of delineating classical and non-classical boundary with simpler nontrivial quantum system.